In a W-CDMA (Wideband-Code Division Multiple Access) mobile communication system, a receiving device (mobile station, for example) is configured to perform despreading processing on a W-CDMA signal transmitted from a base station, as shown in FIG. 10, and to calculate a downlink radio quality by use of a CPICH (Common Pilot Channel) signal thus acquired.
In the W-CDMA mobile communication system, for example, the receiving device is configured to calculate a downlink radio quality by performing averaging processing by use of (Formula 1) below, on receiving qualities rn and rn+1 of two pilot symbols sn and sn+1 which are transmitted consecutively in a time axis direction.
                    [                  Numerical          ⁢                                          ⁢          Expression          ⁢                                          ⁢          1                ]                                                                                                λ              1                        =                                          1                /                2                            ⁢                                                          ⁢                              N                s                            ×                                                ∑                  1                  Ns                                ⁢                                                                                                                        r                        n                                            +                                              r                                                  n                          +                          1                                                                                                                          2                                                              ⁢                                          ⁢                      λ            2                    =                                    1              /              2                        ⁢                                                  ⁢                          N              s                        ×                                          ∑                1                Ns                            ⁢                                                                                                            r                      n                                        -                                          r                                              n                        +                        1                                                                                                              2                                                    ⁢                                  ⁢                  RSRP          =                                    1              /              2                        ×                                                                          λ                  1                                -                                  λ                  2                                                                                  ⁢                                  ⁢                  ISSI          =                      λ            2                                              (                  Formula          ⁢                                          ⁢          1                )            
Herein, “RSRP” denotes a reception power of a required signal, and “ISSI” denotes a received power of an interference signal. In addition, “rn=αSn+In” and “rn+1=βSn+1+In+1” hold true, where each of “α” and “β” denotes an amplitude shift and a phase shift which arise due to a fading effect on the corresponding one of the transmitted symbols, and each of “In” and “In+1” denotes an interference wave component including thermal noise of the corresponding symbol.
In this regard, in the W-CDMA mobile communication system, two pilot symbols transmitted consecutively on a time axis at a single frequency are used for calculation of the downlink radio quality. In a case where transmission channels of these two pilot symbols can be regarded as almost the same transmission channel, the coefficients “α” and “β” by which “sn” and “sn+1” are respectively multiplied are regarded as the same. Thereby, highly accurate estimation of a power is possible in this case.